Methods Of Moulding

Description

Methods Of Moulding

As has already been said, it is necessary that the patternmaker should have some knowledge of moulding in order that he may construct his patterns so that they can easily be removed from the Band. A brief description of the general method employed will suffice.

Ordinarily, a casting is made in a flask consisting of two parts, each containing its complement of sand. The upper part is called the cope, and the lower part the nowell or drag. The pattern is sometimes made in two pieces that part along the line separating the cope and the drag. Thus in Fig. 105 the pattern separates with the flask, on the line A B; and when so separated, the cope is turned upside down and the portion of the pattern C is lifted out. The part D is lifted out of the drag in the same way.

In the case of moulding a hallow object, the internal cavity- in the casting is formal by at a dry wind core, which rests in impressions made in the used by cere prints attached to, and forming, a part of, the pattern. To illlisrate this, let it be reqirinJ hollow cylinder show* in Fig . The wooden patten necessary to produce this hollow cylinder is shown in Fig, 107, whicli, as will be seen, represent* the cylinder only externally by the part A.

The core prints, one on each end of A, are represented by x and y. These projectionsform part of the pattern,and make thier impressions in the sand with the part A, which alone represent* the required cylinder. The- core box,, in which the dry sand core is formed, is shown in Fig. 108, The length of the inside of the box will be the extreme length of the pattern including x and y, and the inside width will be the exact diameter of the core prints.

Fig. 105.

Fig. 106.

Fig. 107.

In this case, the core being a cylinder, only a half core box (Fig. 108) is used. In it are made two semi-cylindrical cores, which, after being dried, are cemented together, thus forming the complete cylindrical core required.

To mould this halved or parted pattern, as it is called, the upper half of the pattern is laid on the moulding board, and the drag is turned over it with the bottom side of the drag up and the parting side on the moulding board, as shown in Fig. 109, After being "rammed up," the drag and moulding board are turned over and the board removed, when the parting of the pattern will be exposed, the half pattern being imbedded in the wind.

Fig. 108.

BAND SAW.

Diliver Machinery Company.

The second half of the pattern is now placed in position on the first, and dry parting sand is spread over the surface of the wet or "green" sand; the cope is put in position on the drag, as shown in Fig. 110, and rammed up. Upon the cope and the drag being separated, the sand will separate on the line to which the parting sand has been applied, which, as will be seen, is the line of parting of the cope and the drag, one half of the pattern remaining in each.

Fig. 109.

Fig. 110.

Fig. 111.

After the pattern has been removed (one half from the cope, and the other half from the drag), the completed dry sand core is placed in the moulds made by the core prints x and y. This core B is shown in position in Fig. Ill and entirely of the -and y, itself of the mould made by A, room for the metal to is to form the required cylinder. '" 'he above cylinder it is not necessary that the parted (made in two halves) as shown in Fig, 107. Patterns for small work, and even for large castings, are often made in one piece, as shown in Fig. 112. To mould this solid pattern it is placed on the moulding board with sufficient sand to keep it from rolling, and the drag is inverted over it as before. When the drag has been rammed up, it is turned over, and will then present the appearance shown in Fig. 113, the entire pattern being embedded in the sand. The sand is now cut away and removed, as shown in Fig. 114, down to the center line of the pattern. The cut sand is smoothed; and, after dry parting sand has been applied to the surface of the wet Band, the cope is placed in position and rammed up as usual. Upon the cope being removed, the sand will part along the lines d e and c d, leaving one-half of the entire pattern exposed. The pattern can now be lifted out, the core placed in position, and the cope returned to its place on the drag, when it is ready for the pouring, as in Fig. 111.

Fig. 112.

Fig. 113.

Fig. 114.

Fig. 115.

Fig. 116.

Another example of a one-piece pattern is the small brass hand wheel shown in Fig, 115. The pattern for this wheel is placed on the moulding board, and the drag inverted over it and rammed up. After the drag has been turned over, the 6and is cut away and removed, not only down to the center of the rim, but also to the center line of the four arms, as shown by the dotted lines in Fig. 116.